The present invention relates to locks in general, and more particularly to improvements in so-called clasp locks or self-locking spring locks which can be utilized to releasably couple the end portions of necklaces, bracelets, chains and/or other articles of jewelry. Still more particularly, the invention relates to improvements in locks of the type wherein the front wall of an elongated hollow receptacle is provided with an opening for introduction of a deformable clasp which can be inserted into the receptacle only upon deformation and is automatically locked in the inserted position in response to relaxation or termination of deforming pressure.
As a rule, the clasp of a conventional clasp lock has a relatively rigid leg and a resilient leg one end portion of which is soldered or welded to one end portion of the rigid leg and the other end portion of which must be depressed toward the rigid leg in order to permit insertion of the clasp into or its extraction from the receptacle. A drawback of such locks is that the cost of the clasp is relatively high, primarily because the two legs must be produced separately to be thereupon soldered or similarly bonded to each other in a time-consuming operation. The problem is aggravated if the clasp is small or very small which is desirable when the lock is used to couple portions of certain types of jewelry, i.e., the lock should be as unobtrusive as possible. In many instances, soldering of the two legs to each other must be followed by manual secondary treatment so as to ensure that the soldered-together end portions of the legs can penetrate into the receptacle by way of the opening in the front wall. Such secondary treatment is necessary for each of a short or long series of clasps, and the finished clasps cannot be used interchangeably (i.e., in conjunction with different receptacles) because, as a rule, each clasp is finished by hand so as to fit only into a particular receptacle.
Soldering of the legs to each other entails many additional problems. Thus, the soldered portion of the clasp is likely to fatigue after a relatively short period of use so that the resilient leg breaks away from the other leg and can cause loss of the article of jewelry whose ends are coupled to each other.
In accordance with another earlier proposal, the clasp is obtained from an elongated blank which is bent in or close to the middle through an angle of approximately 180 degrees to form two legs which partially or fully overlap each other. Such clasps also break in the region of the junction between the two legs due to fatigue of their material after a relatitely short period of use, i.e., after a relatively small number of flexures of one of the legs with reference to the other leg. In addition, the above described clasps must be discarded even in the absence of a total break if the aging or fatigue of their material is sufficiently advanced to prevent return movement of the resilient leg to its normal or unstressed position because return movement to such position is a prerequisite for adequate anchoring of the fully inserted clasp in the receptacle.